In the printing industry, many image enhancement techniques have been introduced in printing systems to improve the quality of printed documents. For example, print quality enhancement (PQE) is a technology that permits one to obtain high-quality printing while using printers with lower resolution than would be required otherwise. The benefits of PQE include reduced edge raggedness, control over boldness, stroke-imbalance correction, and improvements to the appearance of patterns that are difficult to print. Data bandwidth and storage requirements are therefore reduced. Over time, as printer dots per inch (DPI) resolutions have increased and the requirements for high-quality halftone image quality have increased, the need for edge-raggedness improvements have decreased. The emphasis therefore has shifted to using PQE boldness control to adjust halftone dot gain, instead of text boldness.
PQE relies on an imaging system with multiple exposure levels. The same multiple exposure level capabilities required for PQE can be exploited in the latest generations of higher-quality, higher-DPI print engines to produce higher-quality halftone images. These print engines are electro-photographic printers with capabilities as high as 1200 dots per inch (dpi) and 2-bits per spot, for example. The multi-bit capability is an improvement over binary data printers of the past. With binary data, pixels are either white or black. In comparison, the multi-bit capability allows the printer to expose the photoconductor with different intensity levels of light to create exposure that are not just black and white, but something falling in between black and white. For example, a 2-bit per spot printing system corresponds to 4 levels of exposure: a minimum level of exposure of white, a low-level exposure (between white and black), a medium-level exposure (between white and black), and a high-level exposure of black. These multiple levels of exposure can be employed by multi-bit halftones to increase the number of levels of gray that can be achieved for the same halftone design when compared to a binary halftone.
However, integrating PQE with the multi-bit halftone data of these high quality print engines has proven problematic. The problem lies in making systems that traditionally have PQE, which converts binary data to multi-bit data, work with a system that combines binary data and multi-bit halftone data, in such a way that the binary data can exist in a document as a white and full-intensity exposure level with PQE improvements, while co-existing with multi-bit data that is white or black, as well as the intermediate levels of gray. Current systems do not allow such combined data to exist while allowing PQE to be applied to the binary data and not the multi-bit halftone data.
As such, a system that is capable of integrating binary data for PQE purposes with multi-bit halftone data would be beneficial.